Guidelines for Cholera Control Table of Contents Guidelines for Cholera Control World Health Organization
WHO Library Cataloguing in Publication DataGuidelines for cholera control.
1. Cholera - prevention & control - handbooks
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These guidelines have been prepared by the Global Task Force on Cholera Controlof the World Health Organization to help managers of national diarrhoeal diseasecontrol programmes and others responsible for implementing cholera controlactivities. They may also be useful to international, bilateral, andnon-governmental agencies in deciding on appropriate means of assisting countriesto control cholera outbreaks.
The WHO Global Task Force on Cholera Control was created in April 1991, and iscomprised of representatives from the Programme for Control of DiarrhoealDiseases, the Community Water Supply and Sanitation unit, the Food Safetyprogramme, the Strengthening of Epidemiological and Statistical Services unit,the Office of Information, the Microbiology and Immunology Support Services unit,the Office of External Coordination, the Division of Health Education, theDivision of Emergency Relief Operations, and the Action Programme on EssentialDrugs. A staff member of the United Nations Children’s Fund (UMCEF) regularlycontributes to the work of the Task Force.
Additional information may be obtained by contacting the Programme for Control ofDiarrhoeal Diseases, World Health Organization, 1211 Geneva 27, Switzerland. Acknowledgements
The important contributions of WHO’s Community Water Supply and Sanitation unitto this publication are gratefully acknowledged, as are those of the othermembers of the Global Task Force on Cholera Control and the Geneva office of theUnited Nations Children’s Fund (UNICEF).
The laboratory methods described in Annex 5 are based on the Manual forlaboratory investigations of acute enteric infections.
International Centre for Diarrhoeal Disease Research, Bangladesh, Dr Dhiman Baruaformerly of the Programme for Control of Diarrhoeal Diseases, World HealthOrganization, Geneva, Switzerland, Dr Bradford Kay of Johns Hopkins UniversitySchool of Hygiene and Public Health, Baltimore, MD, USA, and Dr Kaye Wachsmuth ofthe Centers for Disease Control, Atlanta, GA, USA assisted in preparing theguidelines.
1Manual for laboratory investigations of acute enteric infections. Geneva, World Health Organization, 1987 (unpublished WHO documentCDD/83.3 Rev. 1, available on request from the Programme for Control
of Diarrhoeal Diseases, World Health Organization, 1211 Geneva 27,Switzerland).
WHO also appreciates the contributions of Dr Paul A. Blake, Dr Mitchell Cohen, DrRoger I. Glass, Dr Allen Ries, Dr Robert Tauxe, Dr Duc Vugia, and Dr Todd Weberof the Centers for Disease Control, Atlanta, GA, USA, Dr Bruce Dick of theInternational Federation of Red Cross and Red Crescent Societies, Geneva,Switzerland, Dr Ann Dawson and Dr Roger Skinner of the Department of Health,London, England, Dr Sandy Cairncross of the London School of Hygiene and TropicalMedicine, London, England, Dr Jamie Bartram of the Robens Institute, Universityof Surrey, Guildford, England, Professor John Pickford of Loughborough Universityof Technology, Loughborough, England, Dr John Kvenberg of the United States Foodand Drug Administration, Washington, DC, USA, and Dr Eugene Rice of the UnitedStates Environmental Protection Administration, Washington, DC, USA, whosesuggestions helped to make this a more practical publication. 1. Introduction
Cholera has spread widely since 1961 and now affects at least 98 countries. Extensive experience has shown that the introduction of cholera into a countrycannot be prevented; its spread within a country, however, can be contained byappropriate control measures.
During the past three decades, intensive research has contributed substantiallyto our understanding of the epidemiology and clinical management of cholera. Itis now known that:
in more than 90% of cases cholera is mild, and may therefore bedifficult to distinguish from other types of acute diarrhoealdisease;
asymptomatic carriers of the disease are common;
improved treatment, in most cases by oral rehydration therapy, canreduce case fatality rates for cholera to less than 1%;
where cholera is present but not epidemic, it causes fewer than 5%of all cases of acute diarrhoea;
vaccination, mass chemoprophylaxis, and cordon sanitaire areineffective in preventing or controlling outbreaks;
care in drinking and eating habits, safe disposal of excreta, andpersonal cleanliness are the most effective ways for individuals toreduce the risk of cholera.
Because cholera can be an acute public health problem, with the potential tospread quickly and cause many deaths, special attention must be given tosurveillance and control. These guidelines provide information to assist nationaldiarrhoea control programmes, emergency task forces, and others in their effortsto control cholera. 2. About cholera
Most cholera infections are mild; patients may have no symptoms or only milddiarrhoea. In a minority of cases, however, there is rapid onset of severe waterydiarrhoea and vomiting, resulting in the loss of large amounts of fluid and saltsfrom the body. Patients become thirsty, stop urinating, and quickly become weakand dehydrated. Patients with severe cholera often complain of cramps in thestomach, arms, or legs.
All cases of cholera should be treated immediately. If treatment is delayed orinadequate, death from dehydration and circulatory collapse may follow veryshortly.
There are more than 60 serogroups of Vibrio cholerae, but only serogroup O1causes cholera. Vibrio cholerae O1 occurs as two biotypes - classical and El Tor. Each biotype also occurs as two serotypes - Ogawa and Inaba. The El Tor biotypehas caused almost all of the recent cholera outbreaks, although cases caused bythe classical biotype still occur on the Indian subcontinent. The El Tor biotypealso causes a higher proportion of asymptomatic infections than the classicalbiotype and survives longer in the environment. It can live in association withcertain aquatic plants and animals, making water an important reservoir forinfection.
Cholera is acquired by the ingestion of an infectious dose of cholera vibrios. Faecally contaminated water is usually the vehicle for transmission of infection,either directly or through the contamination of food. Food may also becontaminated by the soiled hands of infected persons.
The dose of Vibrio cholerae O1 required to produce illness depends on thesusceptibility of the individual. It can be affected by the level of acidity inthe stomach (the vibrio is destroyed at pH 4.5 or lower), and by immunityproduced by prior infection with Vibrio cholerae O1. In endemic areas,breast-feeding protects infants and young children. Box 1. Common sources of infection Drinking-water
that has been contaminated at its source (e.g. by faecally contaminated surfacewater entering an incompletely sealed well) or during storage (e.g. by contactwith hands soiled by faeces), and ice made from contaminated water. Food contaminated during or after preparation
e.g. milk, cooked rice, lentils, potatoes, beans, eggs, and chicken.
particularly shellfish, taken from contaminated water and eaten raw orinsufficiently cooked. Fruit and vegetables
grown at or near ground level and fertilized with night-soil, irrigated withwater containing human waste, or "freshened" with contaminated water, and theneaten raw. 3. Preventing cholera
The only sure means of protection against cholera epidemics are adequate watersupplies and sanitation. 3.1 Ensuring a safe water supply
Access to safe water is a basic requirement for health, made more critical whencholera threatens. Since contaminated water is the usual source of cholerainfection, all efforts must be made to provide safe drinking-water, as well assafe water for food preparation and bathing. The supply of water must be of goodquality, affordable, and available to all - continuously and in sufficientquantity for all domestic purposes. Box 2. Recommended chlorine levels in water distribution systems in areas affected by cholera
The minimum levels of free residual chlorine necessary for safewafer are:
at all sampling points in a piped water system
at standposts in systems with standposts
Active monitoring is required to ensure that these minimumlevels of chlorine are maintained.
In urban areas, properly treated drinking-water should be made available to theentire population through a piped system, at standposts, or from tanker trucks. In rural areas, where there is no source of treated water and where water fromtube wells, protected dug wells, or protected springs is not available, peoplemust be taught that water can be made safe at home by bringing it to a vigorous,rolling boil or by adding a chlorine-releasing chemical.
A supply of suitable chemicals for treating water, and narrow-mouthed pots withcovers for storing water, are helpful in reducing secondary transmission ofcholera within a family. Household filtration of water can also help to eliminatethe vibrio, but should always be followed by disinfection with chlorine or byboiling. (Further information on providing safe water in communities andindividual homes can be found in Fact sheets on environmental sanitation forcholera control.
1Fact sheets on environmental sanitation for cholera control. Geneva,Health World Organization (in preparation). Will be available onrequest from Community Water Supply and Sanitation, World HealthOrganization, 1211 Geneva 27, Switzerland.
Boiling is an effective method of water sterilization, but is not practical forthe needs of most populations, especially when fuel is scarce. The method isexpensive and should be recommended chiefly for emergency situations when thedisinfection of water by chlorination or other methods is not possible. Box 3. Making water safe by boiling
To make water safe for drinking and other uses, bring water to a vigorous,rolling boil and keep it boiling for 1 minute, This will kill, or inactivate,Vibrio cholerae O1 and most other organisms that cause diarrhoea.
Even when drinking-water is safe, infection may still be transmitted bycontaminated surface water used for bathing or for washing cooking utensils. Whensurface water is contaminated, as confirmed by laboratory tests, appropriatemeasures - including closing affected areas - should be taken to reduce thedanger of infection. Indeed, special care should be given to any source of watershown to be contaminated. The water should be made safe or, if this is notpossible, an alternative water source should be provided. Box 4. Making water safe by chlorination The following guidelinesshould be translated intomessages that takeappropriate account oflocally available productsand measuring devices, and ofwhether the instructions arefor home or institutionaluse.Make a stock solution of chlorine (1 % concentration by weight of available chlorine). Add to 1 litre of water:
If products with theseconcentrations of chlorineare not available in thelocal market, adjust theamount used according to theavailable concentrations.
Store the stock solution in acool place in a closedcontainer that does not admitlight. The stock solutionloses effectiveness with timeand must be used no later
than one month after it hasbeen made. Use the stock solution to make safe water. Add water to the stock Solution to ensure proper mixing:
Allow the chlorinated waterto stand for at least 30minutes before using it. Theresidual chlorine level after30 minutes should be between0.2 and 0.5 mg/litre.
If the water is turbid (notclear, with a lot ofsuspended solid matter):
filter itbeforechlorination, or boil itvigorously (asindicated in Box3) instead oftreating it bychlorination. 3.2 Sanitation
Good sanitation can markedly reduce the risk of transmission of intestinalpathogens, including cholera vibrios; this is especially true where the lack ofgood sanitation may lead to contamination of clean water sources. High priorityshould be given to observing the basic principles of sanitary human wastedisposal, as well as to ensuring the availability of safe water supplies.
Appropriate facilities for human waste disposal are a basic need of allcommunities; in the absence of such facilities there is a high risk of cholera. Sanitary systems that are appropriate for the local conditions should beconstructed with the cooperation of the community. (Designs for latrineconstruction in different types of soils and climatic conditions can be found inthe WHO publication, A guide to the development of on-site sanitation.
Annex 1 for instructions on building a ventilated improved pit latrine.)
1Franceys R, Pickford J, Reed R. A guide to the development ofon-site sanitation. Geneva, World Health Organization, 1992.
People will need to be taught how to use latrines, about the dangers ofdefecating on the ground, or in or near water, and about the importance of
thorough hand-washing with soap or ash after any contact with excreta. Thedisposal of children’s excreta in latrines needs to be emphasized.
When large groups of people congregate, for fairs, funerals, religious festivals,etc., particular care must be taken to ensure the safe disposal of human wasteand the provision of adequate facilities for hand-washing. Box 5. Preparing an emergency pit latrine In an emergency, while a more permanent latrine is being built, a simple pit canbe dug as a temporary solution for the disposal of human excreta. It shouldmeasure 0.3 x 0.3 metre, have a depth of 0.5 metre, and be at least 30 metresfrom a well or other source of drinking-water. Where possible, the pit should beat least 6 metres from the nearest house. It should not be located uphill fromthe water source or dug in marshy soil, The bottom of the pit should neverpenetrate the groundwater table.
After each use, a layer of soil should be laid down in the pit. In an areaaffected by cholera, the pit should also be coated each day with a layer ofunslaked lime. 3.3 Food safety
Since food can be an important vehicle for disease organisms, each country shouldestablish adequate controls for the handling and processing of food through anational programme on food safety.
Health education activities, which should be intensified where there is a threatof cholera, should stress the importance of:
avoiding raw food (exception: undamaged fruits and vegetables fromwhich the peel can be removed are safe if hygienically handled);
cooking food until it is hot throughout;
eating food while it is still hot, or reheating it thoroughlybefore eating;
washing and thoroughly drying all cooking and serving utensilsafter use;
handling and preparing food in a way that reduces the risk ofcontamination (e.g. cooked food and eating utensils should be keptseparate from uncooked foods and potentially contaminated utensils);and
washing hands thoroughly with soap (or ash) after defecating, orafter contact with faecal matter, and before preparing or eatingfood, or feeding children. Box 6. WHO Centres for Environmental Health
For additional information and assistance on water supply and sanitationmeasures contact:
Regional Centre for Environmental Health Activities (CEHA)P.O. Box 926967
Centre for Promotion of Environment Planning and Applied Sciences (PEPAS)P.O. Box 12550Kuala Lumpur 50782Malaysia
Centro Panamericano de Ingenieria Sanitaria y Ciencias del Ambiente (CEPIS)Casilla 4337Lima 100Peru
WHO Collaborating Centre for Environmental and Epidemiological Aspects ofDiarrhoeal DiseasesDepartment of Epidemiology and Population SciencesLondon School of Hygiene and Tropical MedicineKeppel StreetLondon WC1E 7HTEngland
WHO Collaborating Centre for Water Quality and Human HealthRobens InstituteUniversity of SurreyGuildfordSurrey GU2 5XHEnglandorCommunity Water Supply and SanitationWorld Health Organization1211 Geneva 27Switzerland
Street food-vendors and restaurants may pose a special risk during an epidemic. Environmental health workers, or their equivalent, must be especially vigilant ininspecting food-handling practices. They should be given the authority to stopstreet sales or close restaurants when their inspections reveal insanitarypractices.
Houseflies play a relatively small role in spreading cholera, but their presencein large numbers indicates poor sanitary conditions which favour transmission ofthe disease. 4. Being prepared for a cholera epidemic
A strong programme for the control of diarrhoeal diseases (CDD) is the bestpreparation for a cholera epidemic, both in areas that have not yet been affectedand in areas where seasonal recurrence of the disease may be expected. In thelong term, improvements in the water supply and in sanitation are the best meansof preventing cholera. In an outbreak, however, the best control measures are theearly detection and treatment of people with cholera, and health education.
In an unprepared community, cholera can cause death in as many as 50% of severecases. However, where health facilities are well organized, with trained staffand essential supplies, fatalities among patients presenting for treatment may beless than 1%. Sections 4.1 to 4.3 outline the elements that are considered to beof paramount importance if a national CDD programme is to be adequately preparedto control an outbreak of cholera. 4.1 Training in clinical management of patients with acute diarrhoea
In an active national CDD programme, medical and paramedical personnel receiveintensive and continuing training to ensure that they are familiar with the mosteffective techniques for management of patients with acute diarrhoea, includingcholera. WHO provides materials for clinical management training, which emphasizepractice in assessing and treating patients with diarrhoea.
1Diarrhoea management training course: guidelines for conductingclinical training courses at health centres and small hospitals. Geneva, World Health Organization, 1990 (unpublished WHO documentCDD/SER/90.2, available on request from Programme for Control ofDiarrhoeal Diseases, World Health Organization, 1211 Geneva 27,Switzerland).
The assessment and treatment procedures for cholera are essentially the same asfor diarrhoea from other causes (see Annex 2). 4.2 Emergency stocks of essential supplies
In order to respond quickly to an epidemic of cholera and to prevent deaths fromthe disease, health facilities must have access to adequate quantities ofessential supplies/ particularly oral rehydration salts, intravenous fluids, andappropriate antibiotics.
During a cholera epidemic, these supplies may be suddenly needed in greaterquantities than normal. To prepare for an outbreak, it is therefore essential tomaintain additional stocks at appropriate points in the drug delivery system. Small ’’buffer stocks" may be placed at local health facilities, larger bufferstocks at district or provincial levels, and an adequate emergency stock at acentral distribution point.
The buffer stocks are additional to the supplies needed to meet normal demands:they are not specifically set aside for a cholera outbreak, but they allow thedistribution system to absorb sudden increases in the demand for specificsupplies. The buffer stocks are put into the normal delivery system so thatstocks are rotated sufficiently often to avoid their becoming outdated. (Forguidance in estimating required supplies, see section 5.4.)
4.3 Surveillance and reporting
An adequate disease surveillance system facilitates the early detection ofcholera, especially when daily records are maintained of diarrhoea cases seen inhealth facilities and by health workers in the community. A cholera outbreakshould be suspected if:
a patient older than 5 years develops severe dehydration or diesfrom acute watery diarrhoea; or
there is a sudden increase in the daily number of patients withacute watery diarrhoea, especially patients who pass the "rice water"stools typical of cholera.
When such changes in the pattern of diarrhoea occur, health workers shouldimmediately notify the nearest referral facility or the designated local healthofficer, if possible by telephone or radio. They should specify the name,address, and age of each patient, and the date the illness began. Members ofvoluntary organizations, religious leaders, students, and other community memberscan also be encouraged to help in detecting and reporting cases.
When this information comes from an area where cholera has not previously beenconfirmed, bacteriological and epidemiological investigations should be promptlyarranged to determine the cause of the outbreak. The manager of the national CDDprogramme or the epidemic control unit should be informed immediately, so thatappropriate control measures can be initiated. 5. Early responses to the threat of an outbreak
Countries with fully established CDD programmes have trained healthprofessionals, disease surveillance systems, rehydration and other treatmentsupplies in health facilities, and continuing health education activities. Programmes in various government ministries and departments work together toimprove water supply, sanitation, and food safety practices. When a choleraoutbreak occurs, these activities need to be reinforced and applied to control ofthe disease. If measures to control cholera and other types of diarrhoea are notyet established, efforts must be made to implement them. In addition, theactivities outlined in sections 5.1 to 5.5 should be initiated. 5.1 Notification according to International Health Regulations
Under the terms of the International Health Regulations of 1969,
of three diseases for which it is mandatory to notify the World HealthOrganization. National health authorities should report the first suspected casesof cholera on their territory to WHO as rapidly as possible. Laboratoryconfirmation should be obtained at the earliest opportunity and also reported toWHO. 1International Health Regulations (1969), 3rd ed. Geneva, WorldHealth Organization, 1983.
Health authorities in countries where cholera is confirmed should make a weekly report to WHO, containing - as a minimum - the numbers of new cases and deaths since the last report and the cumulative totals for the current year, recorded by region or other suitable geographical division. Information on the age distribution of cases and the number admitted to hospital is also desirable. This information should be sent simultaneously to the appropriate WHO Regional Office and to WHO Headquarters in Geneva (telex 415 416 or telefax 41.22.791 07 46, attention: EPIDNATIONS). Box 7. Definition of cholera cases for international reporting A case of cholera should be suspected when:
in an area where the disease is not known to be present, apatient aged 5 years or more develops severe dehydration or dies
in an area where there is a cholera epidemic, a patient aged 5
develops acute watery diarrhoea, with or without
1For management of cases of acute watery diarrhoea inan area where there is a cholera epidemic, cholerashould be suspected in all patients aged 2 years ormore. However, the inclusion of all cases of acutewatery diarrhoea in the 2-4 year age group in thereporting of cholera greatly reduces the specificity ofreporting. A case of cholera is confirmed when: Vibrio cholerae O1 is isolated from any patient with diarrhoea.
When cholera is newly suspected in an area, the International Health Regulationsrequire that the diagnosis should be confirmed by laboratory investigations assoon as possible. Once the presence of cholera in an area has been confirmed, itbecomes unnecessary to confirm all subsequent cases. Neither the treatment northe notification of suspected cases of cholera requires laboratory confirmationof the presence of Vibrio cholerae O1. Monitoring of an epidemic should, however,include laboratory confirmation of a small proportion of cases on a continuingbasis.
Unfortunately, some countries do not report cases for fear that restrictions maybe imposed on exports and on travel by their citizens, or that tourism may beaffected. Officials reluctant to report cases should bear in mind thatnotification often facilitates negotiations for removing trade and travelrestrictions, and promotes international collaboration in the control of cholera. 5.2 National coordinating committee
A national CDD programme, coordinated by a programme manager, is usuallyresponsible for activities related to cholera control. The far-reaching effectsof a cholera epidemic often also call for a national coordinating committee,reinforced by senior members from other relevant departments and ministries, toensure full collaboration among the involved sectors and the rapid execution ofcontrol activities. This committee functions as a national cholera controlcommittee, responsible for:
epidemic preparedness; coordination among sectors; regional and international collaboration; collection and reporting of information on cholera cases anddeaths; organization of any necessary special training; procurement, storage, and distribution of required supplies; and implementation, supervision, monitoring, and evaluation of controlactivities.
Depending on the size of the country and on its health service structure, similarcommittees may be created at sub-national or more peripheral levels.
Alternatively, some countries may have a national health emergency committee,which is responsible for controlling all epidemics and other health emergencies. The manager of the national CDD programme should be a member of this committee inorder to facilitate the coordination of activities required for cholera control. In the event that no such committees exist when a cholera outbreak threatens, aninterministerial committee or special task force, with appropriatedecision-making authority, should quickly be formed to carry out the coordinatingfunctions described above.5.3 Mobile control teams
If a cholera outbreak occurs or threatens in countries or areas where theperipheral health services are inadequate or have no experience in controllingthe disease, mobile teams may need to be formed at the national, provincial, ordistrict level, and be trained to:
establish and operate temporary treatment centres;
provide on-the-spot training in case management for local healthstaff;
supervise appropriate environmental sanitary measures anddisinfection;
carry out health education activities and disseminate informationto the public to prevent panic;
arrange for an epidemiological study to establish, if possible, themode of disease transmission involved in the outbreak;
collect stool and environmental specimens, including suspectedfoods, for submission to a bacteriology laboratory; and
provide the required emergency logistic support, such as deliveryof supplies, to health facilities and laboratories.
The members of each team - who may be otherwise employed in public healthservices, hospitals, laboratories, or elsewhere - should be brought together forbriefing on emergency activities, their individual responsibilities, the locationof their supplies, and the situations in which the teams’ services would beneeded. 5.4 Supplies and equipment
Buffer and emergency stocks of essential supplies should already be in placebefore an epidemic starts (see section 4.2). It is important to establish asystem to monitor their use and ensure their prompt replacement. Emergency supplyrequirements should be determined and individuals assigned to coordinate theirprocurement and distribution. The national coordinating committee or task forceis responsible for controlling the provision of supplies and equipment byexternal agencies, if necessary, to ensure that all drugs and materials meetnational standards and requirements, and to avoid duplication of requests. Asingle central system for recording all incoming supplies and their distribution
to different parts of the country is desirable.
The supplies and equipment needed for 100 cases of cholera are listed in Box 8. To estimate the number of cases that can be expected in a country or areaaffected by a cholera epidemic, an attack rate of 0.2% can be used (i.e. 200cases may be expected to occur in a population of 100 000). In a severe epidemic,the national attack rate may be 1.0% or higher, and may reach 10 - 20% in someareas. However, calculations based on an attack rate of 0.2% should allow enoughsupplies to meet needs during the first weeks of the epidemic, during which timethe requirements can be reassessed. Box 8. Estimated minimum supplies needed to treat 100 patients during a cholera outbreak Rehydration supplies
1The supplies listed are sufficient for intravenousfluid followed by oral rehydration salts for 20 severelydehydrated patients, and for oral rehydration saltsalone for the other 80 patients.
650 packets oral rehydration salts (for 1 litre each)
2If Ringer’s lactate solution Is unavailable, normalsaline may be substituted,
3 nasogastric tubes, 5.3 mm OD, 3.5 mm ID (16 French), 50 cm long,for adults
3 nasogastric tubes, 2.7 mm OD, 1.5 mm ID (8 French), 38 cm long,for children
60 capsules doxycycline, 100 mg (3 capsules per severelydehydrated patient)
480 capsules tetracycline, 250 mg (24 capsules per severelydehydrated patient)
300 tablets trimethoprim-sulfamethoxazole, TMP 20 mg + SMX 100 mg(15 tablets per severely dehydrated patient)
If selective chemoprophylaxis is planned, the additional requirements for fourclose contacts per severely dehydrated patient (about 80 people) are:
240 capsules doxycycline, 100 mg (3 capsules per person)
1920 capsules tetracycline, 250 mg (24 capsules per person)
Other treatment supplies
2 large water dispensers with tap (marked at 5- and 10-litrelevels) for making ORS solution in bulk 20 bottles (1 litre) for oral rehydration solution (e.g. empty IVbottles) 20 bottles (0,5 litre) for oral rehydration solution 40 tumblers, 200 ml 20 teaspoons 5 kg cotton wool 3 reels adhesive tape
5.5 Emergency treatment centres
Simplified treatment is the most important advance in cholera control and meansthat effective treatment can be within the immediate reach of most patients. Manydeaths can thus be prevented, and the excellent results obtained also serve tocalm public fears.
Most cases can be treated in existing health centres if rehydration materials(oral rehydration salts and intravenous fluid) and antibiotics are available, andhealth workers are trained in the management of diarrhoea.
If appropriate facilities, supplies, and trained staff are unavailable or are faraway, or if there are too many cases to be handled by existing facilities, itwill be necessary to establish emergency treatment facilities in affectedcommunities. Temporary facilities can be established in huts, school buildings,or tents, and can be provided with the necessary supplies and trained staff.
These facilities, set up to provide rapid and efficient treatment for a largenumber of patients, should not be used to quarantine them: quarantine does nothelp to control the epidemic. Furthermore, while it is advisable to restrictcontact between patients and the surrounding community to a minimum, it is notnecessary to apply strict isolation measures, such as face masks, gloves, orspecial clothing for health staff and visiting family members. As in any unittreating patients with a communicable disease, it is important to have convenienthand-washing facilities for people working with and visiting cholera patients. The safe disposal of excreta and vomit is essential (see section 7.2). 6. Management of the patient with cholera
Prompt recognition of cholera cases is important in order to start treatment asearly as possible and to reduce potential contamination of the environment. Cholera should be suspected when:
a patient older than 5 years develops severe dehydration from acutewatery diarrhoea (usually with vomiting); or
any patient older than 2 years has acute watery diarrhoea in anarea where there is an outbreak of cholera.
Early case recognition also permits infected household contacts to be identifiedand helps the epidemiologist to investigate how cholera is being spread so thatspecific control measures can be implemented.
Patients must be treated as rapidly as possible, to reduce the risk of shock. Forthis reason, all patients with cholera should seek treatment from a trainedhealth worker. During epidemics, when there are many cases but few healthworkers, grouping cholera patients in a single centre can facilitate treatmentand also help to reduce environmental contamination. 6.1 Rehydration therapy
The dehydration, acidosis, and potassium depletion typical of cholera result fromthe loss of water and salts through diarrhoea and vomiting. Rehydration therapyconsists of replacing water and salts in the proportions lost. Because largevolumes of fluid may be rapidly lost, frequent reassessment during and afterrehydration is essential until the diarrhoea stops.
While preparing to go to a health facility for treatment, patients with cholerashould immediately start increasing the amount of fluids they drink. Sugar-saltsolution and other fluids available in the home, including water, can be used toprevent or delay the onset of dehydration on the way to the health facility. However, these measures are inadequate for treating dehydration caused by acutediarrhoea, particularly cholera, in which the stool loss and risks of shock areoften high. Where available for use in the home, oral rehydration salts (ORS)solution can also be taken from the onset of diarrhoea.
At the health facility, 80 - 90% of cholera patients can usually be adequatelytreated with ORS solution alone, without intravenous therapy. The composition ofORS solution approximates the water and salts contained in the diarrhoeal stool. Prepackaged ORS is the most suitable product for use in remote areas; whensupplies are scarce, ORS packets should be reserved for this purpose. Inhospitals and health centres, where large volumes are consumed daily, ORSsolution can be made from packets or by weighing out the individual ingredientsin appropriate quantities for the required volumes. A rice-based ORS solution mayalso be prepared (see Box 9).
Patients with cholera require intravenous rehydration more often than patientswith diarrhoea due to other causes. Even in cholera, however, intravenouselectrolyte solutions should be used only for the initial rehydration of severelydehydrated patients, including those who are in shock. Ringer’s lactate solution(Hartmann’s solution for injection) is the preferred fluid for intravenousrehydration. Its composition is suitable for treating patients of all ages andwith all types of diarrhoea. (Some specially prepared poly-electrolyte solutionsare also suitable, but are less widely available.)
Normal saline solution is somewhat less effective for intravenous rehydration,but can be used if Ringer’s lactate solution is unavailable. Plain glucosesolutions are ineffective and should not be used.
Cholera patients started on intravenous therapy should be given ORS solution assoon as they can drink, even before the initial intravenous therapy has beencompleted. They should then be treated with ORS solution until diarrhoea stops. After rehydration, patients should also be permitted to drink water.
For further information on rehydration therapy, see Annex 2. 6.2 Feeding the cholera patient
Food should be given after 3-4 hours of treatment, when rehydration is completed. Breast-feeding of infants and young children should be continued. Box 9. To make 10 litres of ORS solution from bulk ingredients
1To make 10 litres ofrice-based ORS solution,boil 500 grams of ricepowder in 11 litres ofwater for 5 minutes, (Theextra litre allows forwater lost during boiling,)Cool the liquid, Add 35grams sodium chloride, 29grams trisodium citrate (or25 grams sodiumbicarbonate), and 15 gramspotassium chloride. Mixwell. Rice-based ORSsolution should be usedwithin 8-12 hours, afterwhich fresh solution shouldbe prepared.
In 10 litres of water, completelydissolve the sugar and salts in theamounts shown below. Use the usualdrinking-water. Boiled water, cooledbefore use, or chlorinated water isbest. If larger volumes are prepared,the amount of each ingredient should beincreased proportionally. ORS solutionshould be used within 24 hours; afterthat time, unused solution should bediscarded and fresh solution prepared. 6.3 Antibiotics
In severe cases of cholera, antibiotics can reduce the volume and duration ofdiarrhoea, and shorten the period during which cholera vibrios are excreted. Theycan be given orally as soon as vomiting stops, usually within 3-4 hours afterstarting rehydration. There is no advantage in using injectable antibiotics,which are expensive.
The patients who benefit most from antibiotics are those who are severelydehydrated. Indiscriminate use of antibiotics in mild cases can quickly use upsupplies and hasten the development of antibiotic resistance among choleravibrios.
For adult cholera patients, doxycycline, a long-acting form of tetracycline, isthe preferred antibiotic because only a single dose is needed. For children,paediatric tablets or liquid preparations of trimethoprim-sulfamethoxazole(TMP-SMX) are recommended. A single dose of doxycycline has not yet been shown tobe effective in children. Tetracycline, however, is effective in children but insome countries is not available for paediatric use. Furazolidone, erythromycin,and chloramphenicol are other effective alternatives for adults and children. (See Table 3 of Annex 2 for antibiotics used in treating severe cholera.)
Sulfadoxine is not effective, and should not be used. A single dose can causeserious and even fatal reactions.
The choice of antibiotic should take into account local patterns of resistance toantibiotics. Knowledge of antibiotic sensitivity patterns of recent isolates inthe immediate area or in adjacent areas is therefore important. Antibiotic-resistant Vibrio cholerae O1 should be suspected if diarrhoeacontinues after 48 hours of antibiotic treatment. No antidiarrhoeal, anti-emetic, antispasmodic, cardiotonic, or corticosteroid drugs should be used to treat cholera. Blood transfusions and plasma volume expanders are not necessary. 7. Preventing the spread of an outbreak
People contract cholera from drinking water or eating food contaminated withcholera organisms. Prevention is based on reducing the chances of ingestingvibrios. When cholera appears in a community, efforts must be intensified topromote the sanitary disposal of human waste, the provision of safe water, andsafe practices in handling food (see section 3). In addition, the measuresdescribed in sections 7.1 to 7.3 should be implemented. 7.1 Health education
Health education is the key to public awareness and cooperation. An outbreak canbe more quickly controlled when people understand how to help limit its spread. Experienced health educators therefore play an important role in epidemiccontrol. Community and service organizations can also be useful in disseminatinghealth messages through their programmes.
It is particularly important to inform people that most cases of cholera can betreated with simple measures, and that vaccination is not effective. There is nosubstitute for drinking only safe water, practising good personal hygiene, andpreparing food safely. (See Annex 3 for examples of appropriate health educationmessages.)
7.2 Disinfection and funeral precautions
In unhygienic living conditions, contamination of a cholera patient’ssurroundings is almost inevitable. A patient’s bedding and clothing can bedisinfected by stirring them for 5 minutes in boiling water. Bedding, includingmattresses, can also be disinfected by thorough drying in the sun. Moreover, inorder to minimize contamination of the washing area, the patient’s clothing andother articles can be disinfected by drying them in the sun before washing. Box 10. Key points for public education about cholera To prevent cholera
Drink only water from a safe source or water that has beendisinfected (boiled or chlorinated).
Cook food or reheat it thoroughly, and eat it while it is stillhot.
Avoid uncooked food unless it can be peeled or shelled.
Wash your hands after any contact with excreta and beforepreparing or eating food.
Dispose of human excreta promptly and safely. Remember
With proper treatment, cholera is not fatal.
Take patients with suspected cholera immediately to a healthworker for treatment.
Give increased quantities of fluids (if available, oralrehydration salts solution), as soon as diarrhoea starts.
Cholera vaccination is not recommended.
Appropriate treatment of cholera stools also helps to control the spread of anepidemic. The simplest method for a family or small rural health unit to disposeof cholera stools is by putting them in a pit latrine or by burying them.
In larger health facilities, safe treatment and disposal of liquid waste fromcholera patients, including excreta and vomit, can be accomplished bysterilization or burial. Stools and vomit from cholera patients can be mixed withdisinfectants (e.g. cresol). Hospitals can use a prepared acid solution to mixwith the waste to lower it to a pH below 4.5. After 15 minutes it is generallysafe to dispose of this mixture in a toilet or latrine, or by burying it. Excessive quantities of acid should not be used to lower the pH more thannecessary. Furthermore, the toilet and other installations must becorrosion-resistant (e.g. made of ceramic material), or extensive damage to thesewage system can result. Acid should not be used when hospital sewage is drainedto a septic tank, because it will interfere with and damage the functioning ofthe tank.
The preferred method for disposing of semisolid waste is incineration, providedthat the incinerator used is designed to destroy contaminated waste. Semisolidwaste from cholera patients should be kept separate from other kinds of wasteand, if possible, put into single-use, moisture-proof bags. If the waste istransported from its initial storage point to an on-site incinerator by means ofhandcarts, this equipment must be cleaned regularly and used only fortransporting waste. The bags used to gather and carry the waste should also beburned. If the waste is transferred for treatment outside the health facility,the transport vehicle should have an enclosed, leak-proof body, which should becleaned after each use and disinfected regularly. Box 11. Some public health supply requirements
Chlorine chemicals for water treatment (gas chlorine, sodiumhypochlorite, calcium hypochlorite, bleaching powder, and chlorinetablets)
DPD (diethyl-p-phenylenediamine) water testing kits for measuringresidual chlorine levels
Funerals for people who die of cholera - or of any other cause in a communityaffected by cholera - can contribute to the spread of an epidemic. Funerals maybring people from uninfected areas into an infected area from which they cancarry the cholera organism back home. It is therefore important to make everyeffort, through intensive health education or by legislation, to limit funeralgatherings, ritual washing of the dead, or funeral feasts. To reduce the spreadof infection, funerals should be held quickly and near the place of death.
Those who care for and clean up after the cholera patient, and especially thosewho prepare the body (which may include cleaning the large bowel), can be exposedto high concentrations of vibrios. These are often the same people who thenprepare large quantities of food for others who attend the funeral. Discouragingthese practices can substantially reduce the risk of the transmission ofinfection. If funeral feasts cannot be cancelled, and if other people are notavailable to prepare the food, meticulous hand-washing with soap and clean wateris essential before food is handled. A designated health worker, present at thefuneral gathering, can be helpful in supervising the use of hygienic practices. 7.3 Ineffective control measures
Efforts to control cholera through mass chemoprophylaxis, vaccination, and traveland trade restrictions are ineffective. When cholera threatens, however, pressureto use these measures may come from a frightened public or from uninformedofficials. National policies on appropriate control measures are therefore vitaland should be developed before an outbreak occurs. 7.3.1 Chemoprophylaxis
Treatment of an entire community with antibiotics, referred to as masschemoprophylaxis, has never succeeded in limiting the spread of cholera. There
are a number of reasons for this failure:
It usually takes longer to organize distribution of the drug thanfor the infection to spread.
The effect of the drug persists for only a day or two, after whichreinfection can occur.
To prevent reinfection, the entire population would need to betreated simultaneously and then isolated.
It may be difficult to persuade people who are symptom-free to takea drug.
Mass chemoprophylaxis not only fails to prevent the spread of cholera, but alsodiverts attention and resources from effective measures. In several countries, ithas also contributed to the emergence of antibiotic resistance in the vibrio,depriving severely ill patients of a valuable treatment. Selective chemoprophylaxis may be useful for members of a household, who sharefood and shelter with a cholera patient. However, in an outbreak of El Torcholera, secondary cases may be unusual. Moreover, in societies where intimatesocial mixing and the exchange of food between households are common, it isdifficult to determine who is a close contact.
The value of selective chemoprophylaxis thus depends on local circumstances. Itis justified only if surveillance shows that the secondary attack rate in thecommunity is high, i.e. that an average of at least one household member in fivebecomes ill after the first case occurs in the household.
If selective chemoprophylaxis is used, it should be given to all close contactsas soon as possible after the initial case is recognized. The prophylactic doseof antibiotic is the same as the therapeutic dose (see Annex 2). Doxycline ispreferred because only a single dose is needed. 7.3.2 Vaccination
For a number of reasons, the vaccine currently available is of no help incontrolling cholera. Field trials have shown that:
the vaccine frequently lacks the required potency;
even when potent, the vaccine is not very effective - that is, notall persons who are vaccinated are protected;
any protection that does occur lasts for only 3-6 months; and
vaccination does not reduce the incidence of asymptomaticinfections or prevent the spread of infection.
In addition, vaccination can give a false sense of security to people who havebeen vaccinated and to health authorities, who may then neglect more effectivemeasures. Vaccination campaigns divert resources and manpower from more usefulcontrol activities.
Because of the limitations of cholera vaccination, the Twenty-sixth World HealthAssembly (1973) abolished the requirement in the International Health Regulationsfor a certificate of vaccination against cholera. No country currently requires
travellers to have a cholera vaccination certificate. 7.3.3 Travel and trade restrictions (cordon sanitaire)
Travel and trade restrictions between countries or different areas within acountry do not prevent the spread of cholera. Even the most concentrated effortscannot detect and isolate all infected travellers, most of whom have no signs ofillness. Moreover, a cordon sanitaire requires check-posts to be set up andmovements to be restricted. These activities divert substantial human and otherresources from more effective control measures.
As well as being ineffective, restrictions on travel and trade severely disruptthe economy of a country or area and, as a result, encourage the suppression ofinformation regarding cholera outbreaks. Collaboration between local, national,and international authorities in their joint efforts to control cholera outbreaksmay thus be severely hampered. Box 12. Risk of cholera transmission through food trade
1Adapted from a Statement by the Global Task Force on CholeraControl to the 44th World Health Assembly (10 May 1991)
Vibrio cholerae O1 can survive on a variety of foodstuffs for up to 5 days atambient temperature and up to 10 days at 5 - 10 C. The organism can alsosurvive freezing. Low temperatures, however, limit proliferation of the organismand thus may prevent the level of contamination from reaching an infective dose.
The cholera vibrio is sensitive to acidity and drying, and commercially preparedacidic (pH 4.5 or less) or dried foods are therefore without risk. Gammairradiation and temperatures above 70 C also destroy the vibrio, and foodsprocessed by these methods, according to the standards of the CodexAlimentarius, are safe unless subsequently contaminated.
The foods that cause greatest concern to importing countries are seafood andvegetables that may be consumed raw. Cases of cholera have occurred as a resultof eating food, usually seafood, transported across international borders byindividuals.
However, a large number of tests carried out on commercially imported foods fromaffected countries (most recently from South America) have not detected Vibriocholerae O1. Indeed, although individual cases and clusters of cases have beenreported, WHO has not documented a significant outbreak of cholera resultingfrom commercially imported food.
In summary, although there is a theoretical risk of cholera transmissionassociated with international food trade, the weight of evidence suggests thatthis risk is small and can normally be dealt with by means other than an embargoon importation. 8. Epidemiology: investigating an outbreak
At the start of a cholera outbreak, even as general control measures are applied,epidemiological studies can determine the magnitude of the outbreak and the modeof transmission, so that more specific and effective control measures can beapplied. Recording the time and place of suspected and confirmed cases,preferably on a spot map, can help identify sources and routes of infection.
Case-control studies, although difficult to conduct and interpret, may help todefine the mode of transmission, particularly in newly affected areas. Countriesmay request assistance from WHO or other outside sources to conduct them. Laboratory analysis of samples of suspect water, sewage, and food may also behelpful.
During cholera outbreaks in newly affected areas, people of all ages may contractthe disease. However, the more mobile members of the community (usually adults)are more frequently affected because of their greater exposure to possiblesources of contamination, such as food or drinks taken outside the home. Incontrast, a preponderance of cases in children suggests that the disease isendemic in the area. 9. The role of the laboratory
Successful treatment of cholera does not depend on the results of laboratoryexaminations. However, laboratory analysis of specimens from the first suspectedcases is essential to confirm the presence of cholera and determine thecharacteristics of the organism; control measures can then be implemented.
A sufficient number of stool specimens should be examined to identify thecausative organism and test its sensitivity to antibiotics. Once the presence ofcholera is confirmed, it is not necessary to examine specimens from all cases orcontacts. In fact, this should be discouraged since it places an unnecessaryburden on laboratory facilities and is not required for effective treatment. Box 13. Diagnostic laboratory supplies for presumptive identification of Vibrio cholerae O1 at a peripheral laboratory
100 rectal swabs500 g Cary-Blair medium3 x 300 g TCBS medium
250 g trypticase250 g sodium taurocholate2 x 250 g gelatin25 g potassium tellurite
25 g sodium desoxycholate5 g tetramethyl-p-phenylenediamine hydrochloride250 g Kligler’s iron agar500 g nutrient agar5 x 2 ml polyvalent 0-group 1 cholera diagnostic antiserum1 kg Bacto-peptone culture medium500 Petri dishes (9 cm)1000 test-tubes (13 x 100 mm)1000 disposable Bijou bottles
Environmental sampling, including the use of Moore swabs for night-soil andsewage samples, can help clarify how infection is being spread.
Local laboratories that normally undertake bacteriological cultures should becapable of culturing and identifying Vibrio cholerae O1, using the methodsoutlined in Annex 5. They should stock the necessary supplies of media andantisera, and be able to provide transport media and rectal swabs to the
fieldworkers who will collect the specimens.
The laboratory must keep clinicians and epidemiologists promptly informed of allresults. National laboratories may contact WHO to arrange for technicalcooperation with reference laboratories, for example to verify laboratoryfindings or to characterize an atypical strain. 9.1 Handling of stool samples
Stool specimens or rectal swabs from suspected cases should be promptly submittedfor laboratory examination in a transport medium (e.g. Cary-Blair medium), asupply of which should be stocked by the local health centre or health officer. (Techniques for collecting specimens are described in Annex 5.) If a transportmedium is not available, a cotton-tipped rectal swab can be soaked in the liquidstool, placed in a sterile plastic bag, tightly sealed, and sent to thelaboratory. Ideally, specimens should be collected before any antibiotics aregiven to the patients.
The name, age, and address of the patient, the main clinical signs, and the dateand time when the specimen was obtained should be written on a request slip andsent with each specimen. 9.2 Reference laboratory
In areas at risk, a national reference laboratory should be assigned theresponsibility for providing culture media and essential antisera, trainingworkers in local and regional laboratories in appropriate isolation techniques,and monitoring the quality of laboratory services.
The reference laboratory should be able to identify, biotype, and serotype Vibriocholerae O1, and perform antibiotic sensitivity testing. For more complicatedprocedures (e.g. phage typing and toxin testing), it may refer to an appropriateinternational reference laboratory. Box 14. Some International Reference Laboratories
The following centres have facilities for isolating and identifying Vibriocholerae O1, enterotoxin testing, phage typing, and ribotyping. Training in thelaboratory diagnosis of enteropathogens, including cholera, and other technicalassistance can be arranged. The centre should be consulted before strains aresent.
WHO Collaborating Centre for Research, Training and Control in DiarrhoealDiseasesInternational Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR.B)G.P.O. Box 128Dhaka 100Bangladesh
WHO Collaborating Centre for Diarrhoeal Diseases Research and TrainingNational Institute of Cholera and Enteric DiseasesP-33, CIT Road Scheme XMBeliaghataP.O. Box 177Calcutta 700 016India
WHO Collaborating Centre for Phage-Typing and Resistance of EnterobacteriaCentral Public Health Laboratory
Division of Bacterial DiseasesEnteric Disease BranchCenter for Infectious DiseasesCenters for Disease ControlAtlantaGA 30333USA
10. After an outbreak
As an outbreak of cholera subsides, emphasis should shift from emergency controlmeasures to preparedness for future outbreaks and long-term efforts to improvethe safety of public water supplies and sanitation facilities.
Public health education programmes must continually stress the principles of goodpersonal hygiene, and the importance of using only safe water, of the safedisposal of excreta, and of safe food practices.
Ideally, a water supply system in urban areas should provide potable water underconstant positive pressure through a system piped into private homes. The watershould be treated with an effective chemical such as chlorine. Properly operatedfacilities for disposing of excreta in all households are a goal towards whichall local authorities should strive.
In rural areas, water sources should be protected from surface contamination, andlatrines should always be situated so as to drain away from water sources andcatchment areas. The installation of simple devices such as tube wells should beencouraged.
Cholera will ultimately be brought under control only when water supplies,sanitation, personal hygiene, and food handling practices are safe enough toprevent the transmission of Vibrio cholerae O1. Additional information on cholera control
Unless otherwise noted, the publications below are available in English only. A guide on food safety for travellers. Geneva, World Health Organization, 1991(unpublished WHO document WHO/FOS/ 91.1).
This leaflet describes what travellers should do to avoid illnessescaused by unsafe food and drink, and what to do if they getdiarrhoea. Available from Distribution and Sales, World HealthOrganization, 1211 Geneva 27, Switzerland.
Arabic, English, French, German, Spanish (Chinese, Italian,Japanese versions in preparation). Cholera - basic facts for travellers. Geneva, World Health Organization, 1992(unpublished WHO document).
This leaflet is aimed at those travelling to countries where choleraoccurs. It explains what cholera is and how, through simpleprecautions, it can be avoided. Available from Distribution andSales, World Health Organization, 1211 Geneva 27, Switzerland.
Cairncross S. Small scale sanitation. London, London School of Hygiene andTropical Medicine, 1988.
This text provides detailed and illustrated instructions for buildingbasic latrines and water supply systems for families and smallcommunities. It is written especially for community health workersand others with no training in this technical area. Diarrhoea management training course: guidelines for conducting clinical trainingcourses at health centres and small hospitals. Geneva, World Health Organization,1990 (unpublished WHO document CDD/SER/90.2).
This training package includes a Participant Manual, InstructorGuide, a set of slides, and a video tape for use in a 3-4 daytraining course in diarrhoea case management for physicians, nurses,and other health workers. Participants learn through writtenexercises, drills, and practical experience how to assess and treatpatients with diarrhoea, including cholera. The course can beconducted in a health facility wherever there are sufficient numbersof diarrhoea patients available for the practical training. Becauseno special facilities are required, it is ideal for training healthworkers in the field and, where a cholera epidemic threatens, fortraining those responsible for establishing emergency treatmentfacilities. Available on request from the Programme for Control ofDiarrhoeal Diseases, World Health Organization, 1211 Geneva 27,Switzerland. Fact sheets on environmental sanitation for cholera control. Geneva, World HealthOrganization (in preparation.)
Fact sheets on appropriate measures to improve environmentalsanitation for prevention of cholera epidemics. The emphasis is onthe interventions that will result in the best use of existingfacilities, and on disinfection of water. Information from severaltechnical manuals is brought together in a set of brief, easy-to-useinstructions. Will be available on request from Community WaterSupply and Sanitation, World Health Organization, 1211 Geneva 27,Switzerland. Guidelines for drinking-water quality, Vols 1-3. Geneva, World HealthOrganization, 1984-1985.
The guidelines include: Vol. 1, Recommendations; Vol. 2, Healthcriteria and other supporting information; Vol. 3, Drinking-watercontrol in small-community supplies. They are intended for use bycountries as a basis for the development of standards to ensure thesafety of drinking-water supplies. (Second edition in preparation.)
Arabic, Chinese, English, French, Russian. Management of the patient with cholera. Geneva, World Health Organization, 1991(unpublished WHO document WHO/CDD/ SER/91.15 Rev 1).
This document is reproduced in Annex 2. It is also available onrequest from the Programme for Control of Diarrhoeal Diseases, WorldHealth Organization, 1211 Geneva 27, Switzerland.
English, French, Spanish (Portuguese version in preparation). Management of the patient with diarrhoea: supervisory skills course. Geneva,World Health Organization, 1990 (unpublished WHO document).
This training module is designed for use in courses for supervisorsof health workers. It uses written exercises and case examples topresent elements of the management of patients with diarrhoea,including cholera. Available on request from the Programme forControl of Diarrhoeal Diseases, World Health Organization, 1211Geneva 27, Switzerland. Manual for laboratory investigations of acute enteric infections. Geneva, WorldHealth Organization, 1987 (unpublished WHO document CDD/83.3 Rev 1).
Available on request from the Programme for Control of DiarrhoealDiseases, World Health Organization, 1211 Geneva 27, Switzerland.
Rajagopalan S, Schiffman MA. Guide to simple sanitary measures for the control ofenteric diseases. Geneva, World Health Organization, 1974.
Instructions for building latrines and simple water supply systems,including information that would be especially useful under emergencyconditions in hospitals, schools, and refugee camps. A chapter onfood sanitation provides guidelines for safe handling of food duringits production, processing, and preparation for consumption. Tablesidentify the chemicals needed by those responsible for chlorinatingwater and disinfecting contaminated articles.
Franceys R, Pickford J, Reed R. A guide to the development of on-site sanitation. Geneva, World Health Organization,1992.
This publication describes all practical options for on-sitesanitation, that is, means for dealing with excreta where they aredeposited rather than through sewerage systems. It outlines thefoundations of sanitary practice and provides details on the design,construction, and maintenance of various types of latrines, privies,and septic tanks. The planning and development of on-site sanitationprojects are addressed, and the book also includes references,selected further readings, and a useful glossary of terms.
English (French and Spanish versions in preparation). The treatment and prevention of acute diarrhoea: practical guidelines, 2nd ed. Geneva, World Health Organization, 1989.
This book is designed for use by community health workers to helpthem assess dehydration and treat patients with diarrhoea. It alsocontains ideas for encouraging practices that will help to preventdiarrhoea. (Third edition in preparation.)
Chinese, English, French, Portuguese, Russian, Spanish. Annex 1. Building a ventilated improved pit latrine
1For more specific instructions see Cairncross S. Small scalesanitation. London, London School of Hygiene and Tropical Medicine,1988.
A ventilated improved pit latrine is a practical means of disposing of humanexcreta and may be a good solution for use in rural areas. However, the decisionon the type of latrine to be selected should take account of local factors suchas type of soil and density of population.
The latrine must be constructed at least 30 metres away from a well or othersource of drinking-water and, where possible, 6 metres away from a house. Itshould not be located uphill from the water source or dug in marshy soil.
A latrine 2 metres deep with an opening 1 metre x 1 metre can be used by a familyof five for 2-4 years. (This assumes an accumulation rate of between 60 and 100litres per person per year.) To keep bad odours and flies to a minimum,ventilation for this type of pit latrine is provided by an external verticalvent, topped by a fly screen. The edges of the pit are higher than ground levelto prevent rain or other water from draining into it. The latrine should have aconcrete or wooden slab which should reach to the walls of the superstructure. Where possible, concrete reinforced with steel wires at least 8 mm in diameterand 150 mm apart should be used because of its durability and resistance.
The slabs and floor should be washed clean daily and disinfected regularly withcresol or bleaching powder. After the pit is loaded to two-thirds of its capacity(1.3 metres height), it should be filled with soil and compacted, and a new pitshould be dug. Annex 2. management of the patient with cholera
a patient older than 5 years develops severe dehydration from acutewatery diarrhoea (usually with vomiting); or
any patient above the age of 2 years has acute watery diarrhoea inan area where there is an outbreak of cholera.Steps in the management of suspected cholera
Step 1. Assess the patient for dehydration. Step 2. Rehydrate the patient, and monitor frequently. Then reassesshydration status. Step 3. Maintain hydration: replace continuing fluid losses untildiarrhoea stops. Step 4. Give an oral antibiotic to the patient with severedehydration. Step 5. Feed the patient. Step 1. Assess the patient for dehydration
Use Table 1 to determine whether the patient has:
severe dehydration some dehydration no signs of dehydration. Table 1. Assessment of the diarrhoea patient for dehydration *Restless, *Lethargic or irritable* unconscious; floppy* *Thirsty, drinks *Drinks poorly or eagerly* not able to drink*
If the patient has two signs of dehydration or more signs, including
one *sign*, there is some dehydration
aIn adults and children older than 5 years, other
* signs* for severe
dehydration are * absent radial pulse* and * low blood pressure*. The
skin pinch may be less useful in patients with marasmus (severewasting) or kwashiorkor (severe malnutrition with oedema), or obesepatients. Tears are a relevant sign only for infants and youngchildren. Step 2. Rehydrate the patient, and monitor frequently; reassess hydration status For severe dehydration: Give IV fluid immediately to replace fluid deficit. Use Ringer’slactate solution or, if not available, normal saline.
Start IV fluid immediately. If the patient can drink, begin givingoral rehydration salts (ORS) solution by mouth while the drip isbeing set up. For patients aged 1 year and older, give 100 ml/kg IV in 3 hours,as follows:
- 30 ml/kg as rapidly as possible (within 30 minutes);then- 70 ml/kg in the next 2 hours. For patients aged less than 1 year, give 100 ml/kg IV in 6 hours,as follows:
- 30 ml/kg in the first hour; then- 70 ml/kg in the next 5 hours. Monitor the patient very frequently. After the initial 30 ml/kghave been given, the radial pulse should be strong (and bloodpressure should be normal). If the pulse is not yet strong, continueto give IV fluid rapidly. Give ORS solution (about 5 ml/kg per hour) as soon as the patientcan drink, in addition to IV fluid. Reassess the patient after 3 hours (infants after 6 hours), usingTable 1:
- If there are still signs of severe dehydration (this israre), repeat the IV therapy. - If there are signs of some dehydration, continue asindicated below for some dehydration. - If there are no signs of dehydration, go on to Step 3to maintain hydration by replacing continuing fluidlosses. For some dehydration: Give ORS solution in the amount recommended in Table 2. If thepatient passes watery stools or wants more ORS solution than shown,give more. Monitor the patient frequently to ensure that ORS solution is takensatisfactorily and to detect patients with profuse and continuingdiarrhoea who will require closer monitoring. Reassess the patient after 4 hours, using Table 1:
- If signs of severe dehydration have appeared (this israre), treat as in Step 1, above.
- If there is still some dehydration, repeat theprocedures for some dehydration, and start to offer foodand other fluids.
- If there are no signs of dehydration, go on to Step 3to maintain hydration by replacing continuing fluidlosses. Table 2. Approximate amount of ORS solution to give in the first 4 hours Less than 4 5-14 years
aUse the patient’s age only when you do not know the weight. Theapproximate amount of ORS required (in ml) can also be calculated bymultiplying the patient’s weight (in kg) by 75. Notes on rehydration
Most patients absorb enough ORS solution to achieve rehydration even when theyare vomiting. Vomiting usually subsides within 2-3 hours, as rehydration isachieved.
A nasogastric tube should be used for ORS solution if the patient has signs ofsome dehydration and cannot drink, or for severe dehydration only if IV therapyis not possible at the treatment facility.
Urine output decreases as dehydration develops, and may cease. It usually resumeswithin 6-8 hours after starting rehydration. Regular urinary output (every 3-4hours) is a good sign that enough fluid is being given. For no signs of dehydration:
Patients first seen with no signs of dehydration can be treated at home. Give ORS packets to take home. Give enough packets for 2 days. Demonstrate how to prepare and give the solution. The care-givershould give the patient the following amount of ORS solution:
Instruct the patient or the care-giver to return if the patientdevelops any of the following signs:
- increased number of watery stools- eating or drinking poorly- marked thirst- repeated vomiting;or if any signs indicating other problems develop:- fever- blood in stool. Amount of solution after each loose stool ORS packets Step 3. Maintain hydration; replace continuing fluid losses until diarrhoea stops
When a patient who has been rehydrated with IV fluid or ORS solution isreassessed, and has no signs of dehydration, continue to give ORS solution tomaintain normal hydration. The aim is to replace stool losses as they occur withan equivalent amount of ORS solution. Amount of solution, after each loose stool
The amount of ORS solution actually required to maintain hydrationvaries greatly from patient to patient, depending on the volume of
stool passed. The amount required is greatest in the first 24 hoursof treatment, and is especially large in patients who present withsevere dehydration. In the first 24 hours, such patients require anaverage of 200 ml of ORS solution per kg of body weight, but some mayneed as much as 350 ml/kg. Continue to reassess the patient for signs of dehydration at leastevery 4 hours to ensure that sufficient ORS solution is being taken. Patients with profuse continuing diarrhoea require more frequentmonitoring. If signs of some dehydration are detected, the patientshould be rehydrated as described on pages 42 and 43, beforereceiving treatment to maintain hydration.
A few patients, whose continuing stool output is very large, may havedifficulty in drinking the volume of ORS needed to maintainhydration. If such patients become tired, vomit frequently, ordevelop abdominal distension, ORS solution should be stopped andhydration should be maintained intravenously with Ringer’s lactatesolution or normal saline; 50 ml/kg should be given in 3 hours. Afterthis, it is usually possible to resume treatment with ORS solution. Keep the patient under observation, if possible, until diarrhoeastops, or is infrequent and of small volume. This is especiallyimportant for any patient who presented with severe dehydration.
If a patient must be discharged before diarrhoea has stopped, showthe care-giver how to prepare and give ORS solution, and instruct himor her to continue to give ORS solution, as above. Also instruct thecare-giver to bring the patient back if any of the signs listed onpage 44 should develop. Step 4. Give an oral antibiotic to the patient with severe dehydration
An effective antibiotic can reduce the volume of diarrhoea in patients withsevere cholera and shorten the period during which Vibrio cholerae O1 isexcreted. In addition, it will usually stop the diarrhoea within 48 hours, thusshortening the period of hospitalization. Start antibiotics after the patient has been rehydrated (usually in4-6 hours), and vomiting has stopped.
There is no advantage in using injectable antibiotics, which areexpensive. No other drugs should be used in the treatment of cholera.
Use Table 3 to select the antibiotic and dose. Step 5. Feed the patient Resume feeding with a normal diet when vomiting has stopped. Continue breast-feeding infants and young children. Table 3. Antibiotics used to treat cholera Antibiotic Children
aErythromycin or chloramphenicol may be used when the antibioticsrecommended are not available, or where Vibrio cholerae O1 isresistant to them. bDoxycycline is the antibiotic of choice for adults (except pregnantwomen) because only one dose is required. c TMP-SMX is the antibiotic of choice for children. Tetracycline isequally effective; however, in some countries it is not available forpaediatric use. dFurazolidone is the antibiotic of choice for pregnant women. Complications Pulmonary oedema is caused by giving too much IV fluid, especially when metabolicacidosis has not been corrected. The latter is most likely to occur when normalsaline is used for IV rehydration and ORS solution is not given at the same time. When the guidelines for IV rehydration are followed, pulmonary oedema should notoccur. ORS solution never causes pulmonary oedema. Renal failure may occur when too little IV fluid is given, when shock is notrapidly corrected, or when shock is allowed to recur, especially in persons abovethe age of 60 years. Renal failure is rare when severe dehydration is rapidlycorrected and normal hydration is maintained according to the guidelines. Annex 3. Sample health education messages
The following sample messages may be adapted to local conditions and translatedinto local languages. Three simple rules for cholera prevention
1. Cook your food2. Boil your water3. Wash your hands
Are you protected from cholera? Do you prepare food safely? Cooking kills cholera germs
Thoroughly cook all meats, fish, and vegetables. Eat them while they are hot. Washing protects from cholera
Wash your hands before preparing or serving food. Wash your dishes and utensils with soap and water. Wash your cutting board especially well with soap and water. Peeling protects from cholera
Eat only fruits that have been freshly peeled, such as orangesand bananas. Keep it clean - cook it, peel it, or leave it Are you protected from cholera? Is your water boiled or treated?
Even if it looks clean, water can contain cholera germs. Water can be made safe in several ways: Boiling kills cholera germs: boil all drinking-water. Chlorine kills cholera germs: use 3 drops of chlorine solution in1 litre of water. Mix well, and let it sit for half an hour beforedrinking. To make the chlorine solution: mix 3 level tablespoons (33 grams) of
bleaching powder in 1 litre of water. 1This quantity is for a bleaching powder that contains 30%concentration by weight of available chlorine. The quantity to berecommended must be adapted for the bleach available on the localmarket. Drink safe water Are you protected from cholera? Is your water stored safely?
Clean water can become contaminated again if it is not stored safely.
Water should be stored in a clean container with a small opening anda cover. It should be used within 24 hours.
Pour the water from the container - do not dip a cup into the container. Keep it clean - store water safely Are you protected from cholera? Do you wash your hands?
Most dirt that causes cholera is invisible, It can be carried on handswithout you knowing it. Always wash your hands:
after you use the toilet or latrine, or clean up your children before you prepare food before you eat and before you feed your children. What is the best way to wash your hands?
Wash all parts of your hands - front, back, between the fingers,under the nails. Keep it clean - wash your hands Are you protected from cholera? Do you use a toilet or latrine?
Cholera germs live in faeces. Even a person who is healthy may havecholera germs in the faeces. Always use a toilet or latrine. If you don’t have one - build one.
Keep the toilet or latrine clean. Dispose of babies’ faeces in the toilet or latrine (or bury them). Wash your hands with soap (or ash) and clean water after using thetoilet or latrine. Keep it clean - use a toilet or latrine Are you prepared for cholera? What should you do if you get it? Cholera can be treated.
The biggest danger of cholera is loss of wafer from the body. Don’t panic - but act quickly,
Drink oral rehydration salts (ORS) mixed with safe water(boiled orchlorinated).
Go immediately to the health centre. Continue drinking asyou go,
Now - before you or your family get cholera - find out where you canget ORS and how to mix the solution. Annex 4. Rules for safe food preparation to prevent cholera
1Adapted from Annex 6, Golden rules for safe food preparation, ofHealth surveillance and management procedures for food-handlingpersonnel: report of a WHO Consultation. Geneva, World HealthOrganization, 1989 (WHO Technical Report Series, No. 785). 1. Cook raw foods thoroughly
In an area affected by cholera, many raw foods, most notably fish, shellfish, andvegetables, are often contaminated with cholera bacteria. Thorough cooking willkill the bacteria, but remember that the temperature of all parts of the foodmust reach at least 70 C. Do not eat uncooked foods, unless they can be peeledor shelled. 2. Eat cooked foods immediately
When cooked foods cool to room temperature, bacteria begin to grow. The longerthe wait, the greater the risk. To be on the safe side, eat cooked foods as soonas they come off the heat. When there is a delay between cooking and eating food,as when food is sold in restaurants or by street vendors, it should be kept at 60C or more, over heat, until it is served. 3. Store cooked foods carefully
If you must prepare foods in advance or want to keep leftovers, be sure to storethem in a refrigerator or ice-box below 10 C or in an efficient hot-box keptcontinuously above 60 C. This rule is of vital importance if you plan to storefoods for more than four or five hours. Cooked foods that have been stored mustbe thoroughly reheated before eating. Foods for infants should be eatenimmediately after being prepared, and should not be stored at all.4. Reheat cooked foods thoroughly
Reheating foods thoroughly before eating is your best protection against bacteriathat may have grown during storage. (Proper storage at low temperatures slowsdown the growth of bacteria but does not kill them.) Once again, thoroughreheating means that all parts of the food must reach at least 70 C. Eat foodwhile it is still hot. 5. Avoid contact between raw foods and cooked foods
Safely cooked food can become contaminated through even the slightest contactwith raw food. This cross-contamination can be direct, as when raw fish comesinto contact with cooked foods. It can also be indirect. For example, do notprepare a raw fish and then use the same unwashed cutting surface and knife toslice cooked food. Doing so can reintroduce all the potential risks of illnessthat were present before cooking. 6. Choose foods processed for safety
Many foods, such as fruits and vegetables, are best in their natural state. However, in an area affected by cholera they may not be safe unless they havebeen processed. Canned, acidic, and dried foods should be without risk. Whenshopping, keep in mind that food processing was invented to improve safety aswell as to prolong shelf-life. 7. Wash hands repeatedly
Wash hands thoroughly before you start preparing food and after everyinterruption - especially if you have to "change" or clean up the baby or haveused the toilet or latrine. After preparing raw foods, such as fish or shellfish,wash your hands again before you start handling other foods. 8. Keep all kitchen surfaces clean
Since foods are so easily contaminated, any surface used for food preparationmust be kept absolutely clean. Think of every food scrap, crumb or spot as apotential source of bacteria. Cloths used for washing or drying food preparationsurfaces, dishes, and utensils should be changed every day and boiled beforereuse. Separate cloths for cleaning the floors also require daily washing. 9. Use safe water
Safe water is just as important for food preparation as for drinking. If you haveany doubts about the water supply, bring water to a rolling boil before adding itto food that will not be further cooked, or making ice for drinks. Be especiallycareful with any water used to prepare an infant’s meal. When chlorine tabletsare available, they may be used instead of boiling to make water safe. Annex 5. Isolation of Vibrio cholerae O1 in a peripheral laboratory Vibrio cholerae O1, the causative agent of cholera, can be isolated andidentified in any laboratory that has the basic equipment and supplies forbacteriological investigations. The vibrios are present in large numbers in thestools of patients with cholera before antibiotic therapy. They grow easily andrapidly on a variety of selective and non-selective alkaline media.
The following guidelines describe a simple and rapid method for the isolation andidentification of Vibrio cholerae O1 in diarrhoeal stools.
1For instructions on how to isolate Vibrio cholerae O1 fromasymptomatic carriers, and water, sewage, or food samples, see theManual for laboratory investigations of acute enteric infections(Geneva, World Health Organization, 1987: unpublished WHO documentCDD/83.3 Rev 1, available on request from the Programme for Controlof Diarrhoeal Diseases, World Health Organization, 1211 Geneva 27,Switzerland). This manual also describes additional tests tocharacterize Vibrio cholerae O1, identify atypical isolates, anddistinguish Vibrio cholerae O1 from other vibrios and vibrio-likeorganisms. A5.1 Collection and transport of faecal samples
Collect the stool sample before the patient is given an antibiotic. Use a cleancotton-tipped swab, and introduce it well into the rectum. When this is doneproperly, the swab will become moist and may be faecally stained.
Alternatively, collect freshly passed liquid stool in a bottle or on acotton-tipped swab.
If it is possible to be certain that the sample will reach the laboratory within2 hours, put the rectal swab or liquid stool into a sterile screw-cap bottle;seal the bottle tightly for transport.
If, however, the specimen will not reach the laboratory within 2 hours, put itinto a tube containing Cary-Blair transport medium.
Alkaline peptone water (APW) may also be used if the transport time will notexceed 24 hours. At the laboratory, the specimen should be transferred to a freshtube of APW for enrichment before inoculating solid media (see section A5.2).
When a transport medium is not available, soak strips of blotting paper withliquid stool. Send them to the laboratory in carefully sealed plastic bags toprevent drying.
Transport specimens in refrigerated boxes, if possible, or at ambienttemperature. A5.2 Culture and initial identification of Vibrio cholerae O1 Select and inoculate solid media
Laboratory technicians who are not experienced in identifying vibrios should usea selective medium and, if possible, a non-selective one. As experience is gainedin recognizing typical colonies, the process may be simplified by using only thenon-selective medium.
Satisfactory non-selective media include:
gelatin agar (GA), pH 8.2 to 8.5. Satisfactory selective mediainclude:
thiosulfate citrate bile salts agar (TCBS agar), pH 8.6
Note: TCBS plates should be used within 3 days of being prepared.
taurocholate tellurite gelatin agar (TTGA), pH 8.5.
Instructions on preparing these media are given in section A5.3.
If possible, both the following procedures for inoculating the mediumshould be followed:
(1) Streak the specimen directly onto a non-selective orselective medium, or onto both. Incubate the platesovernight (12-18 hours) at 35-37 C.
(2) Enrich the culture of Vibrio cholerae O1 byinoculating the swab, or by putting 2-3 loopfuls of stoolinto a tube of APW. Incubate the specimen for 6-8 hoursat 35-37C.
Then, inoculate plates from the APW tube and incubate as in (1)above.
If the incubation of APW exceeds 8 hours, inoculate a second tube ofAPW from the first, and repeat the incubation for 6-8 hours beforeinoculating solid media.
If only one procedure is followed, enrichment in APW followed byinoculation of solid media is recommended. Identification of Vibrio cholerae O1 Identify suspicious colonies
Colonies of Vibrio cholerae O1 and Vibrio cholerae non-O1 have the sameappearance:
On MEA, they are colourless, translucent, flat, and 2-3 mm indiameter.
On GA, they appear the same as on MEA, but have a halo.
On TCBS agar, they are yellow, shiny, convex, and 2-3 mm indiameter. (Some strains of Aeromonas have a similar appearance.)
On TTGA, they are translucent, flat, and 1-2 mm in diameter. At 24hours they have dark pinpoint centres; later the colonies becomegun-metal grey. Perform tests to make a presumptive identification of Vibrio cholerae O1 Slide agglutination with specific antisera
Suspicious colonies should be tested for slide agglutination in polyvalent(group) Vibrio cholerae O1 antiserum.
Colonies may be tested directly from MEA, GA, or TTGA media. However, coloniesfrom TCBS agar should not be tested directly because they are difficult toemulsify. Yellow colonies from TCBS agar should first be subcultured on MEA or GAfor serological testing.
If possible, positive reactions should be confirmed with monovalent Ogawa andInaba typing sera. Vibrio cholerae O1 will react with the O1 group antiserum andeither Ogawa or Inaba typing serum.
A rapid presumptive diagnosis of Vibrio cholerae O1 can be attempted by streakingstool heavily on a pre-dried MEA or GA plate. This specimen should be incubatedfor 4-6 hours at 35 - 37 C, and the confluent growth from the plate used to testfor slide agglutination. Other useful tests
Performing the above test with specific antisera is sufficient to diagnose a caseof cholera when clinical and/or epidemiological patterns also suggest thedisease.
However, if the required antisera are not available, the following tests may beused to support the identification of Vibrio cholerae O1, but will notdifferentiate serogroup O1 from other serogroups. String test. Suspend an 18- to 24-hour growth from an MEA, GA, orTTGA plate, or a Kligler’s iron agar (KIA) slant in a drop of 0.5%aqueous solution of sodium desoxycholate on a slide.
When positive, the suspension immediately loses turbidity and becomesmucoid (as with all vibrios). A mucoid "string" forms when the loopis drawn slowly away from the suspension. A few strains of Aeromonasshow a weak string after about 60 seconds. Oxidase test. Use fresh growth from an MEA, GA, or TTGA plate, orthe KIA slant (but not a TCBS agar plate). All Vibrio cholerae (both01 and non-01) are oxidase-positive, as are a number of other
Gram-negative bacteria. However, Enterobac-teriaceae areoxidase-negative. (See section A5.3 for further instructions.)
Kligler’s iron agar (KIA) reaction. Inoculate suspicious coloniesinto a tube of KIA. Vibrio cholerae (both 01 and non-01) produce analkaline (red) slant, acid (yellow) butt, and no hydrogen sulfide orother gas. Some other Gram-negative bacteria also produce thisreaction. Send specimen to a reference laboratory for confirmation
Laboratory diagnosis of Vibrio cholerae O1, as described above, can be completedwithin 24-48 hours in a peripheral laboratory, and is sufficient for mostpurposes. However, when additional studies are desired to confirm cholera or toidentify atypical isolates, these can be done at a reference laboratory. Suchstudies may include serotyping, biotyping, antibiotic sensitivity testing, andbiochemical characterization of suspected Vibrio cholerae O1. They may alsoinvolve identification of atypical strains or related species.
A nutrient agar or trypticase soy agar (TSA) stab should be used to transport thespecimen to a reference laboratory.
Note: In most cases, the specimen would be sent to a national referencelaboratory. Special tests and training for laboratory staff, however, can bearranged with some international reference laboratories (see section 9.2). A5.3 Preparation of media for transporting and isolating Vibrio cholerae O1
Media such as Cary-Blair, TCBS agar, and KIA are best provided to laboratories aspremixed dry ingredients. However, other media can be prepared at the peripherallaboratory, according to the following instructions. (For more information on thecomposition of various media, see Manual for laboratory investigations of acuteenteric infections.)Alkaline peptone water (APW) Preparation. Add ingredients to the water and adjust pH to 8.5 with aconcentrated solution of sodium hydroxide. Dispense in 5-10 ml amounts intoscrew-capped bottles. Autoclave at 121 C for 15 minutes. (Store alkaline mediain bottles with tightly screwed caps to prevent a drop in pH.)
Meat extract agar (MEA) Preparation. Add ingredients to the water and heat to boiling while stirring todissolve the agar. Adjust the pH to 8.5 with a concentrated solution of sodiumhydroxide. Autoclave at 121 C for 15 minutes. Pour plates aseptically (20 ml perplate). Allow plates to cool slowly and store them in an inverted position at 4C. The plates should be used within 3-5 days. Note: On this medium, colonies of Vibrio cholerae O1 are translucent, whereasthose of Enterobacteriaceae are opaque. Gelatin agar (GA) Preparation. Add ingredients to the water and heat to boiling while stirring todissolve the agar. Adjust pH to 8.5 with a concentrated solution of sodiumhydroxide. Dispense into screw-capped bottles. Autoclave at 121 C for 15minutes. Taurocholate tellurite gelatin agar (TTGA) Preparation. Add ingredients to the water and heat to boiling while stirring todissolve the agar. Adjust the pH to 8.5 with a concentrated solution of sodiumhydroxide. Dispense into screw-capped bottles. Autoclave at 121 C for 15minutes.
Before use, add 0.5-1.0 ml of a filter-sterilized 0.1% aqueous solution ofpotassium tellurite to each 100 ml of the melted TTGA medium at 55 C. Mix well. Pour plates aseptically (20 ml per plate). A5.4 Oxidase reagent and test
Oxidase reagent is a 1% solution of tetramethyl-p-phenylenediaminedihydrochloride in distilled water. (1% dimethyl-p-phenylenediamine may also beused in the paper strip test.)
The reagent should be colourless and should be stored in a glass-stoppered, darkbrown bottle, protected from the light, in a refrigerator. If only a clear glassbottle is available, it should be wrapped in aluminium foil or dark paper.
The oxidase test is performed as follows:
Use fresh growth from an MEA, GA, or TTGA plate, or the KIA slant (but not a TCBSagar plate). Place 2-3 drops of the oxidase reagent on a piece of filter paper ina Petri dish. Smear the culture across the wet paper with a platinum (notnichrome) loop or a clean, fine wooden toothpick.
A positive reaction is indicated by the appearance of a dark purple colour on thepaper within 10 seconds. Among the Gram-negative rods. Vibrio, Campylobacter,Aeromonas, Plesiomonas, Pseudomonas, and Alcaligenes are oxidase-positive. AllEnterobacteriaceae are negative.
Test a positive control using a species of Pseudomonas and a negative controlusing a strain of Escherichia coli at the same time. Selected WHO publications of related interest The rational use of drugs in the management of acute diarrhoea in children. 1990 (71 pages) The management and prevention of diarrhoea: practical guidelines. Readings on diarrhoea. Student manual.
Jelliffe DB, Jelliffe EFP. Dietary management of young children with acute diarrhoea. Second edition. 1991 (29 pages) Basic laboratory procedures in clinical bacteriology.
Rajagopalan S, Schiffman MA. Guide to simple sanitary measures for control of enteric diseases. 1974 (102 pages)
Franceys R, Pickford J, Reed R. A guide to the development of on-site sanitation. 1992 (245 pages) Manual of epidemiology for district health management. 1989 (198 pages)
Further information on these and other World Health Organization publications canbe obtained from Distribution and Sales, World Health Organization, 1211 Geneva27, Switzerland,
* Prices in developing countries are 70% of those listed here.
Almost 100 countries worldwide are still affected by cholera and experience hasshown that its introduction into a country is impossible to prevent Unchecked, anoutbreak of the disease rapidly reaches epidemic proportions and may result inmany deaths. However, improved methods for surveillance, diagnosis, andtreatment, coupled with better standards of sanitation and personal hygiene, cansignificantly limit the spread of infection and minimize the public healthproblem.
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